carb help

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carb help

Post  jasonf on July 16th 2012, 1:03 pm

I have a Holley 80508 (750 vac secondary) on my 382 windsor. The snake hooked me up with a new cam last fall and it now has a smidge of a hesitation on tip in and is super rich at an idle. I put a vacuum gauge on it and at idle vac. bounces between from 9-11 inches. I had a 6.5 power valve in and I replaced it with a 4.5. That helped the idle richness tremendously but it is still rich IMO. (I am judging this based on the burning in my nose and eyes Smile ). I had 68 jts in the primary so I just dropped them to 66 to see what effect it will have.

Do the primary jets have any effect on the idle circuit or are they two different systems?
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Re: carb help

Post  rmcomprandy on July 16th 2012, 4:02 pm

jasonf wrote:I have a Holley 80508 (750 vac secondary) on my 382 windsor. The snake hooked me up with a new cam last fall and it now has a smidge of a hesitation on tip in and is super rich at an idle. I put a vacuum gauge on it and at idle vac. bounces between from 9-11 inches. I had a 6.5 power valve in and I replaced it with a 4.5. That helped the idle richness tremendously but it is still rich IMO. (I am judging this based on the burning in my nose and eyes Smile ). I had 68 jts in the primary so I just dropped them to 66 to see what effect it will have.

Do the primary jets have any effect on the idle circuit or are they two different systems?

You have contradicting things happening.
You say it is rich yet it has a hesitation at "off idle".

From what you say here, it does not have near the correct amount of primary throttle opening at idle; there is to much slot showing below the plate.
Open the hidden secondary idle speed screw 1/2 turn and re-adjust it all from there.

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Re: carb help

Post  res0rli9 on July 16th 2012, 5:41 pm

rmcomprandy wrote:
jasonf wrote:I have a Holley 80508 (750 vac secondary) on my 382 windsor. The snake hooked me up with a new cam last fall and it now has a smidge of a hesitation on tip in and is super rich at an idle. I put a vacuum gauge on it and at idle vac. bounces between from 9-11 inches. I had a 6.5 power valve in and I replaced it with a 4.5. That helped the idle richness tremendously but it is still rich IMO. (I am judging this based on the burning in my nose and eyes Smile ). I had 68 jts in the primary so I just dropped them to 66 to see what effect it will have.

Do the primary jets have any effect on the idle circuit or are they two different systems?

You have contradicting things happening.
You say it is rich yet it has a hesitation at "off idle".

From what you say here, it does not have near the correct amount of primary throttle opening at idle; there is to much slot showing below the plate.
Open the hidden secondary idle speed screw 1/2 turn and re-adjust it all from there.


Just where is the hidden secondary idle speed screw

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Re: carb help

Post  jasonf on July 16th 2012, 11:14 pm

res0rli9 wrote:


Just where is the hidden secondary idle speed screw

Good question. I will pull it off tomorrow and check the throttle plate and look for the idle screw.
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Re: carb help

Post  TravisRice on July 17th 2012, 8:04 am

Secondary idle screw is on the under side of the base plate on the same side as the vacuum canister on your 750. Small straight screw driver. Do your self a favor and take it completly out and replace it with a allen head but insert it from the top so future adjustments can be made without taking the carb off. Just my 2 cents

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Re: carb help

Post  LivermoreDave on July 17th 2012, 8:33 am

Is there a chance you have installed a "set screw" in the secondary opening linkage? Are the air bleeds clean? I may be incorrect, is the original primary jet size 66 or 67? Install a vacuum gauge in the car and take a reading during WOT as well while cruising, this will determine the power valve rating. As for adjusting the secondary throttle blade position, take an old worn or less used allen wrench and grind to a blade tip, this will allow you to adjust the secondary blade stop. And yes, IMO primary jetting does affect idle fuel to some extent.

Just another $0.02.
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Re: carb help

Post  jasonf on July 17th 2012, 9:45 am

LivermoreDave wrote:Is there a chance you have installed a "set screw" in the secondary opening linkage? Are the air bleeds clean? I may be incorrect, is the original primary jet size 66 or 67? Install a vacuum gauge in the car and take a reading during WOT as well while cruising, this will determine the power valve rating. As for adjusting the secondary throttle blade position, take an old worn or less used allen wrench and grind to a blade tip, this will allow you to adjust the secondary blade stop. And yes, IMO primary jetting does affect idle fuel to some extent.

Just another $0.02.
Dave.

I have not changed the secondary linkage since I owned it. It had 68's in the primary before but I am the second owner so I am sure it was tuned when the motor was first built because it ran really good (just fat at an idle). The hesitation problem I am having now is since the cam change and I am sure it is just the difference in vacuum signal do to the different cam. I'll put a vacuum gauge on it today and check mid/wot.
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Re: carb help

Post  jbozzelle on July 17th 2012, 5:36 pm

Jason

Didn't it have a vacuum leak on the secondary canister? I thought I remembered that when you were working on it at the race?

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Re: carb help

Post  jasonf on July 17th 2012, 8:47 pm

rmcomprandy wrote:

From what you say here, it does not have near the correct amount of primary throttle opening at idle; there is to much slot showing below the plate.
Open the hidden secondary idle speed screw 1/2 turn and re-adjust it all from there.
You nailed that one Randy. When I pulled the carb off 3/4 of the transfer slot was showing. I adjusted it to 0.060" per my Holley manual and set the idle air mixture screws to 1 turn out. This made a huge improvement in idle quality. It fires right off and idles way smoother, even when cold.

TravisRice wrote:Secondary idle screw is on the under side of the base plate on the same side as the vacuum canister on your 750. Small straight screw driver. Do your self a favor and take it completly out and replace it with a allen head but insert it from the top so future adjustments can be made without taking the carb off. Just my 2 cents

Travis do you know what thread that is so I can get a allen head screw?


LivermoreDave wrote:Is there a chance you have installed a "set screw" in the secondary opening linkage? Are the air bleeds clean? I may be incorrect, is the original primary jet size 66 or 67? Install a vacuum gauge in the car and take a reading during WOT as well while cruising, this will determine the power valve rating. As for adjusting the secondary throttle blade position, take an old worn or less used allen wrench and grind to a blade tip, this will allow you to adjust the secondary blade stop. And yes, IMO primary jetting does affect idle fuel to some extent.

Just another $0.02.
Dave.

You were correct on the jet size. I have two sets of 67 in my jet kit so I am going to assume that is what what in it originally ( I changed them last fall so the memory is a little hazy). The secondary linkage is as stock.

How do you tell if the air bleeds are dirty? Blow through them?

I installed the vacuum gauge and this is what I have. Sorry I don't have a tach in the car so I can't tell you what rpms it idles at.
Idle in park 10.5"
Idle in gear 9"
WOT 3"
At cruise (55 mph) 19"

The secondary plates are fully closed.


jbozzelle wrote:Jason

Didn't it have a vacuum leak on the secondary canister? I thought I remembered that when you were working on it at the race?

Yes John the vacuum gasket was squished out. I fixed that.

The jury is still out on how rich it is at an idle. I bought a LM-2 and before I put it in this afternoon I went to update the firmware and not it won't work. I spent most of the afternoon with Innovative tech trying a few different things but now I will probably have to send it to them to fix it. No It still has a pretty good hesitation when you first step on it though. I'm not sure where to go next.....
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Re: carb help

Post  jc10000rpm on July 17th 2012, 11:36 pm

what size primary squirters do u have it right now. ? you probably need to go up a few sizes

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Re: carb help

Post  69F100 on July 18th 2012, 1:21 am

make sure you have gas coming out of the squirters I have had the little hole get stoped up that goes to the squirters.If all that is good check the gap on the excel pump linkage and make sure it is right you might even have to change the cam for the excel pump it might be squirting to late or not enough.Just something you might want to check also.
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Re: carb help

Post  res0rli9 on July 18th 2012, 5:51 am

jc10000rpm wrote:what size primary squirters do u have it right now. ? you probably need to go up a few sizes

Thats what I did and put a 50cc pump on to fix my hesitation.

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Re: carb help

Post  jasonf on July 18th 2012, 4:28 pm

It has a 31 in it. I went and got a couple bigger sizes and I will try that tomorrow. I checked the pump cam adjustment for play and there is non. Fuel comes out as soon as you touch the throttle as well.
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